Blue is often described as a royal colour and it is a shade that finds favour with Kate Middleton. The Duchess of Cambridge has often been spotted in an azure blue and was seen in that stunning colour again, on Thursday.

Kate Middleton was in attendance at an Olympics-themed exhibition in London, at the National Portrait Gallery, of which she is a patron. The exhibition - Road to 2012: Aiming High exhibition - showcases photographic portraits of athletes and other individuals, working behind the scenes, to make the London 2012 Olympic and Paralympic Games happen, according to the official Web site of the gallery.

Catherine, the Duchess of Cambridge, visited the exhibition in a blue crepe dress designed by Stella McCartney, which she teamed with a pair of black Prada heels. The Duchess looked as stunning as ever in her trademark glossy blow-dry hairdo. Kate, who has developed a reputation for minimal accessories, sported a long gold necklace by renowned French jewellery house Cartier. The necklace, bearing five diamond-studded Olympic hoops, is said to be from Kate's personal collection.

Kate's Blue Dresses of the Past

Kate Middleton and the colour blue have a fashionable history; the Duchess has often been seen wearing different shades of royal blue.

One of the earliest such instances was during her first official appearance with Prince William; this was at St James' Palace, in November 2010, soon after their royal engagement. Kate was seen in blue, again, on the morning after her wedding, in April last year, when walking around Buckingham Palace with William.

In addition, Kate Middleton was seen in blue when on her first overseas trip (to Canada), as a member of the British royal family, last July. The Duchess wore blue - a dress by Canadian designer Erdem Moralioglu - with overlaid lace, for her visit to a centre for homeless young people in Quebec City.

Most recently, earlier this year Kate Middleton wore a stunning teal blue outfit to an Olympics concert and a powder blue tweed coat dress to a children's sporting event in Nottingham last month.

Click Start to check out a slideshow with photographs of Kate Middleton in a variety of blue outfits